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    Types: TextFile
    Names: »ibm6153.4«

└─⟦a0efdde77⟧ Bits:30001252 EUUGD11 Tape, 1987 Spring Conference Helsinki
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.\"$Header: ibm6153.4,v 10.1 86/11/19 10:55:47 jg Exp $
.\"$Source: /u1/X/libibm/doc/man/RCS/ibm6153.4,v $
.\ This file uses -man macros.
.TH IBM6153 4 "31 Mar 1986" "Space overwritten by .AC macro" " " 
.UC 4
.AC 1 0
.SH NAME
ibm6153, apa8 \- IBM 6153 Advanced Monochrome Graphics Display interface
.SH SYNOPSIS
.B "pseudo-device apa8"
.SH DESCRIPTION
The IBM 6153 Advanced Monochrome Graphics Display 
is a 12-inch CRT with gray-white phosphor, driven at 92 Hz interlaced.  It
provides
a monochrome, all-points-addressable, bit-mapped display with 393,216
points on the screen (768 displayable pixels on each of 512 displayable 
lines).
All pixels are directly accessible by the CPU. 
The display adapter provides hardware assist features including a 
write mask to protect bit fields within a byte, a barrel shifter to rotate 
bits within a byte, and a logic unit to combine source bytes before they
are written into the bit map.
.PP
The display adapter is a single PC/AT card installed in the
I/O bus as a sixteen-bit device. The display appears to the system
as two separate memory areas: a 128-kilobyte block of 
system memory (beginning at 0xf4d00000), 
and 16 bytes of I/O space (addressed from 0x160 through 0x16f).  
The 128KB block defines
both the visible frame buffer and the hidden, off-screen memory area.
For each of the 512 scan lines, the first 90 bytes (720 pixels) are
visible; the last 38 bytes (304 pixels) are hidden.
The 16 bytes of I/O space access the display adapter's control registers.
.PP
The display operates in glass tty (the default) mode and window-manager mode:
.IP -
Glass tty mode initialization consists of 
the downloading of a character font
into the adapter card, followed by a cursor home and screen clear.
In this mode, the display driver emulates a smart terminal,
similar to
an IBM 3101, and can be
.IR /dev/console .
.IP -
In window-manager mode, a user-level process, 
such as a window manager, can directly control the display device hardware,
loading picture data, accessing display buffers, etc. 
When a process opens 
.IR /dev/apa8 , 
the kernel switches
console output to another display device, if available, or buffers the
output until later (see 
.IR cons (4)). 
At this point, the display and 
control memory areas are accessible for manipulation by the user program.
Glass tty mode is reentered when 
.I /dev/apa8 
is closed.
.SH FILES
/dev/apa8
.br
/dev/console
.SH "SEE ALSO"
cons(4), ibm5151(4), ibm6155(4), ibmaed(4), keyboard(4), tty(4)
.SH DIAGNOSTICS
None.
.SH ERRORS
The following errors can be returned by the interface:
.TP 12
[ENODEV]
Nonexistent display (on open, close, read, write, or ioctl);
.br
Unavailable display (on open):  user processes are denied access to this
display (see
.IR consoles (5),
.IR setscreen (8)).
.TP
[EIO]
Made an attempt to close a display device that was not open.
.IP [EBUSY] 11
The display has already been opened by a user process.
.SH BUGS
Access to the PC/AT I/O and memory busses through
.I /dev/apa8
is not limited to the apa-8 addresses.